Apparatus for treating metallic melts

ABSTRACT

APPARATUS FOR TREATING A METALLIC MELT, SUCH AS MOLTEN STEEL IN A LADLE IS DISCLOSED. THE APPARATUS INCLUDES AN INNER TUBULAR MEMBER, THROUGH WHICH AN ADDITIVE IS DELIVERED TO WITHIN THE MELT, AND A COAXIALLY DISPOSED OUTER TUBULAR MEMBER, THE ANNULUS BETWEEN THE TWO TUBULAR MEMBERS SERVING AS A PASSAGEWAY FOR GAS DELIVERED TO THE MELT. THE GAS IS INTRODUCED INTO THE MELT THROUGH A POROUS REFRACTORY ELEMENT POSITIONED ABOUT THE ENDS OF THE TUBULAR MEMBERS.

Oct. 26, 1971 G. P. BERNSMANN 3,615,085

APPARATUS FOR TREATING METALLIC MELTS y Filed Feb. 26. 1969 IN VENTOR.

his ATTORNEY United States Patent O 3,615,085 APPARATUS FOR TREATING METALLIC MELTS Gert P. Bernsmann, Pittsburgh, Pa., assigner to Jones & Laughlin Steel Corporation, Pittsburgh, Pa. Filed Feb. 26, 1969, Ser. No. 802,518 Int. Cl. C21c 7/ 00 U.S. Cl. 266-34 T 6 Claims ABSTRACT F THE DISCLOSURE Apparatus for treating a metallic melt, such as molten steel in a ladle is disclosed. The apparatus includes an inner tubular member, through which an additive is delivered to within the melt, and a coaxially disposed outer tubular member, the annulus between the two tubular members serving as a passageway for gas delivered to the melt. The gas is introduced into the melt through a porous refractory element positioned about the ends of the tubular members.

This invention relates generally to apparatus for treating a metallic melt and, more particularly, to method and apparatus for effecting an efilcient and controlled deoxidation of molten steel.

Controlled and uniform deoxidation of molten steel in.

a ladle can be realized by simultaeously delivering to a spot deep within the melt through a lance submerged therein a deoxidant, such as aluminum, and an argon gas stream. Employing the apparatus of the present invention, the deoxidant is maintained out of contact with the .molten steel until it exits from the submerged lance whereupon it dissolves and reacts with the oxygen in the steel. The argon gas stream is passed from the lance to the deoxidant rnelt reaction zone through an inherently porous refractory element or a refractory element made porous by the provision of a plurality of fine passageways therein. The gas issuing from the porous element is in a finely subdivided state, thus promoting the stirring of dissolved, unreacted deoxidant throughout the melt and enhancing removal of deoxidation products to the melt surface. The subdivided gas particles also protect the porous element from overheating and early destruction from the reaction heat generated by the deoxidant and liquid steel.

The present invention is also useful in making additions to molten steel of materials, such as lithium and magnesium, which react violently with the molten steel or which possess high vapor pressures. By submerging the lance within the melt, initial contact and reaction between the additive and the molten steel is constrained to occur at any desired depth, obviating the dangers of a violet surface reaction and the complete oxidation of the additive before it has penetrated the melt to any appreciable degree.

The present invention is also used to make alloy additions to molten steel. Uniform distribution of an alloy throughout a melt is insured by its introduction deep within the melt and the dispersing action of the finely subdivided gas stream.

Preferably, the additive is fed to the molten steel through the lance in the form of a continuous rod so that a controlled feed rate is readily maintained. This permits deoxidation of the melt to be closely controlled so that it can be accurately deoxidized to any desired degree. For purposes of this disclosure, the term rod also includes shapes referred to variously as wire and bar. As-cast rods as well as rods formed by mechanical working are used. In addition, rods formed of particles of an additive or additives held together by a suitable binder are employed. Accordingly, a rod can be homogeneous and comprise a single additive or be heterogeneous and comprise several additives.

An object of the invention is to provide apparatus for simultaneously introducing an additive and finely divided gas stream to metallic melts. Another object of the invention is to provide apparatus for effecting controlled deoxidation of molten steel. Yet another object of the invention is to provide for such controlled deoxidation by simultaneously feeding a deoxidant, in the form of a rod, and argon to the molten steel in a ladle.

These and other objects and advantages of the invention will be more apparent from the following detailed description thereof with reference to the drawing in which:

FIG. 1 is a longitudinal view, partly in section, of a first embodiment of the invention; and

FIG. 2 is a longitudinal view, partly in section, of a second embodiment of the invention.

Referring to FIG. l, a lance embodying the principles of this invention is shown and includes a steel inner tubular member 10 and steel outer tubular member 11 concentric therewith. The annulus 20 between the tubular members is closed oil at the top of member 11 by sealing means 12, comprising packing gland 13 welded to member 11, packing box 14 and packing 15.

A circular flange 16 is secured, as by welding, to the lower ends of tubular members 10 and 11, an opening 17 being provided in the center of the flange in line with the interior of member 10.

A porous head or stone 18 of refractory material, of the type known in the art, is positioned about the lower ends of tubular members 10 and 11. The porous head includes a centrally disposed cylindrical recess 19 forming a shoulder 20 in the head. The porous head is supported on flange 16 by its shoulder 20, and is firmly secured thereto by refractory cement 21.

To provide protection against the action of the molten metal, in which the lance in normal operation is submerged, a refractory sleeve 22 consisting of a plurality of stacked cylindrical tiles 23-23 is provided about the tubular members 10 and 11, extending upwardly of said members from the porous head. The bottommost tile rests on head 18 and the stack is held in place by nut 24 which is threaded onto the exterior of tubular member 11 so as to bear down on washer 25 placed on the topmost tile. ln addition, the joints between the tiles are filled with a refractory cement.

A conduit 26 is tapped into outer tubular member 11 and is in fluid communication with annulus 29. In operation, conduit 26 is attached to a gas source.

Ports 27-27 are provided in outer tubular member 11 in the vicinity of porous head 18 to provide a passageway for gas to flow from annulus 29 into and through said head. Alsog, ports 28-28 are provided in tubular member 10 foi establishing fluid communication between annulus 29 and the interior of member 10, enabling a positive pressure to be applied to said interior, preventing the ingress therein of the fluid in which the lance is submerged.

In employing the apparatus described to deoxidize a molten steel bath, the lance is lowered deep Within the bath, an aluminum rod is fed downwardly from the top of inner tubular member 10, exiting from the bottom thereof through opening 17 and into the molten steel bath whereupon the aluminum reacts with the oxygen in the bath. Simultaneously, argon gas is delivered through conduit 26 into annulus 29. The argon passes from the annulus through ports 27-27 and then through porous head 18 into the melt. The finely subdivided gas emerging from head 18 disperses throughout the bath, promoting stirring of the dissolved unreacted aluminum throughout the bath and removal of deoxidation products to the bath surface. The argon also protects the stopper head from overheating from the heat generated by the reacting aluminum and oxygen.

The argon gas flow rate is maintained at least high enough to establish, through ports 28-28, a pressure within tubular member suiicient to balance t-he pressure Within the bath at the level of the bottom of head 18. Entry of the molten metal into tubular member 10 and the consequent reaction therein of oxygen and aluminum is thereby precluded.

The embodiment of the invention illustrated in FIG. 2, is similar to the embodiment of FIG. 1, and the same reference numerals used in both figures refer to the same features in both. In addition to conduit 26, the embodiment of FIG. 2 has a second conduit 30, tapped into the wall of tubular member 10 and in uid communication with the interior thereof. Conduit 30 is connected to a gas source independent of the source to which conduit 26 is connected and transports gas to the interior of member 10 to establish a positive pressuretherein at least balancing the pressure of the bath at the level where the porous head is positioned.

The provision of a second conduit 30 and independent gas source associated therewith to maintain a suitable back pressure within member 10, enables t-he interior of the latter to be kept isolated from annulus 29 by eliminating the ports 28 provided in the embodiment of FIG. 1 for uid communication between the two. As a result, with the embodiment of FIG. 2, the gas flow rate to the melt through porous head 18 can be varied as desired, without concern for the pressure needed to prevent the entry of the material of the melt into member 10.

I claim:

1. A lance for treating metallic melts comprising an elongated inner tubular member open at the lower end thereof, an outer elongated tubular member disposed about said inner tubular member defining an annulus therebetween, a porous refractory head positioned about the lower ends of said tubular members providing means of egress for uid material from said annulus to the outside of the lance in the vicinity of the lower end of the lance and a refractory sleeve positioned about the outer 4 tubular member, extending upwardly thereof from said porous head.

2. The apparatus of claim 1 including ports in said inner tubular member providing fluid communication between said annulus and the interior of the inner tubular member.

3. The apparatus of claim 2 including iirst conduit means open to said annulus for providing a gas under pressure thereto.

4. The apparatus of claim 1 including an annular ange secured to the bottoms of said inner and outer tubular members, said flange having a central opening in line with the interior of the inner tubular member, an annular shoulder in said porous head, the porous head being supported on said ange by means of said shoulder and ports in said outer tubular member providing iluid communication between said annulus and said porous head.

5. The apparatus of claim 4 including ports in said inner tubular member providing iluid communication between said annulus and the interior of the inner tubular member.

6. The apparatus of claim 5 including rst conduit means open to said annulus for providing a gas under pressure thereto.

References Cited UNITED STATES PATENTS GERALD A. DOST, Primary Examiner U.S. C1. X.R. -51 

